Skip to main content
The Journal of Cell Biology logoLink to The Journal of Cell Biology
. 1967 Aug 1;34(2):555–567. doi: 10.1083/jcb.34.2.555

A STRUCTURAL ANALYSIS OF THE MYELIN SHEATH IN THE CENTRAL NERVOUS SYSTEM

Asao Hirano 1, Herbert M Dembitzer 1
PMCID: PMC2107314  PMID: 6035645

Abstract

The cerebral white matter of rats subjected to a variety of noxious experimental conditions was examined in the electron microscope. Several unusual configurations of the myelin sheath are identified in addition to the usual configuration. These variations include the presence of (a) formed organelles within the inner and outer loops, (b) isolated islands of cytoplasm in unfused portions of the major dense lines, (c) apparently unconnected cell processes between the sheath and the axon, and (d) concentric, double myelin sheaths. A generalized model of the myelin sheath based on a hypothetical unrolling of the sheath is described. It consists of a shovel-shaped myelin sheet surrounded by a continuous thickened rim of cytoplasm. Most of the unusual myelin configurations are explained as simple variations on this basic theme. With the help of this model, an explanation of the formation of the myelin sheath is offered. This explanation involves the concept that myelin formation can occur at all cytoplasmic areas adjacent to the myelin proper and that adjacent myelin lamellae can move in relation to each other.

Full Text

The Full Text of this article is available as a PDF (3.8 MB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. ANDRES K. H. UBER DIE FEINSTRUKTUR BESONDERER EINRICHTUNGEN IN MARKHALTIGEN NERVENFASERN DES KLEINHIRNS DER RATTE. Z Zellforsch Mikrosk Anat. 1965 Feb 24;65:701–712. [PubMed] [Google Scholar]
  2. Aleu F. P., Katzman R., Terry R. D. Fine structure and electrolyte analyses of cerebral edema induced by alkyl tin intoxication. J Neuropathol Exp Neurol. 1963 Jul;22(3):403–413. doi: 10.1097/00005072-196307000-00003. [DOI] [PubMed] [Google Scholar]
  3. BARGMANN W., LINDNER E. UBER DEN FEINBAU DES NEBENNIERENMARKES DES IGELS (ERINACEUS EUROPAEUS L.) Z Zellforsch Mikrosk Anat. 1964 Dec 3;64:868–912. [PubMed] [Google Scholar]
  4. BUNGE M. B., BUNGE R. P., PAPPAS G. D. Electron microscopic demonstration of connections between glia and myelin sheaths in the developing mammalian central nervous system. J Cell Biol. 1962 Feb;12:448–453. doi: 10.1083/jcb.12.2.448. [DOI] [PubMed] [Google Scholar]
  5. BUNGE M. B., BUNGE R. P., RIS H. Ultrastructural study of remyelination in an experimental lesion in adult cat spinal cord. J Biophys Biochem Cytol. 1961 May;10:67–94. doi: 10.1083/jcb.10.1.67. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. HIRANO A., ZIMMERMAN H. M., LEVINE S. THE FINE STRUCTURE OF CEREBRAL FLUID ACCUMULATION. III. EXTRACELLULAR SPREAD OF CRYPTOCOCCAL POLYSACCHARIDES IN THE ACUTE STAGE. Am J Pathol. 1964 Jul;45:1–19. [PMC free article] [PubMed] [Google Scholar]
  7. Hirano A., Levine S., Zimmerman H. M. Experimental cyanide encephalopathy: electron microscopic observations of early lesions in white matter. J Neuropathol Exp Neurol. 1967 Apr;26(2):200–213. doi: 10.1097/00005072-196704000-00002. [DOI] [PubMed] [Google Scholar]
  8. Hirano A., Zimmerman H. M., Levine S. Myelin in the central nervous system as observed in experimentally induced edema in the rat. J Cell Biol. 1966 Dec;31(3):397–411. doi: 10.1083/jcb.31.3.397. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. IKUTA F., ZIMMERMAN H. M. VIRUS PARTICLES IN REACTIVE CELLS INDUCED BY INTRACEREBRAL IMPLANTATION OF DIBENZANTHRACENE. J Neuropathol Exp Neurol. 1965 Apr;24:225–243. doi: 10.1097/00005072-196504000-00005. [DOI] [PubMed] [Google Scholar]
  10. KLATZO I., PIRAUX A., LASKOWSKI E. J. The relationship between edema, blood-brain-barrier and tissue elements in a local brain injury. J Neuropathol Exp Neurol. 1958 Oct;17(4):548–564. doi: 10.1097/00005072-195810000-00002. [DOI] [PubMed] [Google Scholar]
  11. Kerr F. W. The ultrastructure of the spinal tract of the trigeminal nerve and the substantia gelatinosa. Exp Neurol. 1966 Dec;16(4):359–376. doi: 10.1016/0014-4886(66)90104-x. [DOI] [PubMed] [Google Scholar]
  12. Kruger L., Maxwell D. S. Electron microscopy of oligodendrocytes in normal rat cerebrum. Am J Anat. 1966 Mar;118(2):411–435. doi: 10.1002/aja.1001180207. [DOI] [PubMed] [Google Scholar]
  13. LAMPERT P., CARPENTER S. ELECTRON MICROSCOPIC STUDIES ON THE VASCULAR PERMEABILITY AND THE MECHANISM OF DEMYELINATION IN EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS. J Neuropathol Exp Neurol. 1965 Jan;24:11–24. doi: 10.1097/00005072-196501000-00002. [DOI] [PubMed] [Google Scholar]
  14. LEVINE S., STYPULKOWSKI W. Experimental cyanide encephalopathy. AMA Arch Pathol. 1959 Mar;67(3):306–323. [PubMed] [Google Scholar]
  15. LEVINE S., ZIMMERMAN H. M., WENK E. J., GONATAS N. K. Experimental leukoencephalopathies due to implantation of foreign substances. Am J Pathol. 1963 Jan;42:97–117. [PMC free article] [PubMed] [Google Scholar]
  16. LUFT J. H. Improvements in epoxy resin embedding methods. J Biophys Biochem Cytol. 1961 Feb;9:409–414. doi: 10.1083/jcb.9.2.409. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Laatsch R. H., Cowan W. M. A structural specialization at nodes of Ranvier in the central nervous system. Nature. 1966 May 14;210(5037):757–758. doi: 10.1038/210757a0. [DOI] [PubMed] [Google Scholar]
  18. Lee J. C., Bakay L. Ultrastructural changes in the edematous central nervous system. II. Cold-induced edema. Arch Neurol. 1966 Jan;14(1):36–49. doi: 10.1001/archneur.1966.00470070040005. [DOI] [PubMed] [Google Scholar]
  19. MATURANA H. R. The fine anatomy of the optic nerve of anurans--an electron microscope study. J Biophys Biochem Cytol. 1960 Feb;7:107–120. doi: 10.1083/jcb.7.1.107. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. METUZALS J. Ultrastructure of myelinated nerve fibers in the central nervous system of the frog. J Ultrastruct Res. 1963 Feb;8:30–47. doi: 10.1016/s0022-5320(63)80019-2. [DOI] [PubMed] [Google Scholar]
  21. PALAY S. L., McGEE-RUSSELL S. M., GORDON S., Jr, GRILLO M. A. Fixation of neural tissues for electron microscopy by perfusion with solutions of osmium tetroxide. J Cell Biol. 1962 Feb;12:385–410. doi: 10.1083/jcb.12.2.385. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. PETERS A. FURTHER OBSERVATIONS ON THE STRUCTURE OF MYELIN SHEATHS IN THE CENTRAL NERVOUS SYSTEM. J Cell Biol. 1964 Feb;20:281–296. doi: 10.1083/jcb.20.2.281. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. PETERS A. OBSERVATIONS ON THE CONNEXIONS BETWEEN MYELIN SHEATHS AND GLIAL CELLS IN THE OPTIC NERVES OF YOUNG RATS. J Anat. 1964 Jan;98:125–134. [PMC free article] [PubMed] [Google Scholar]
  24. PETERS A. The formation and structure of myelin sheaths in the central nervous system. J Biophys Biochem Cytol. 1960 Oct;8:431–446. doi: 10.1083/jcb.8.2.431. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. PETERS A. The structure of myelin sheaths in the central nervous system of Xenopus laevis (Daudin). J Biophys Biochem Cytol. 1960 Feb;7:121–126. doi: 10.1083/jcb.7.1.121. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Peters A. The node of Ranvier in the central nervous system. Q J Exp Physiol Cogn Med Sci. 1966 Jul;51(3):229–236. doi: 10.1113/expphysiol.1966.sp001852. [DOI] [PubMed] [Google Scholar]
  27. ROSS L. L., BORNSTEIN M. B., LEHRER G. M. Electron microscopic observations of rat and mouse cerebellum in tissue culture. J Cell Biol. 1962 Jul;14:19–30. doi: 10.1083/jcb.14.1.19. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. TORACK R. M., TERRY R. D., ZIMMERMAN H. M. The fine structure of cerebral fluid accumulation. I. Swelling secondary to cold injury. Am J Pathol. 1959 Nov-Dec;35:1135–1147. [PMC free article] [PubMed] [Google Scholar]
  29. UZMAN B. G. THE SPIRAL CONFIGURATION OF MYELIN LAMELLAE. J Ultrastruct Res. 1964 Aug;11:208–212. doi: 10.1016/s0022-5320(64)80104-0. [DOI] [PubMed] [Google Scholar]
  30. UZMAN B. G., VILLEGAS G. M. A comparison of nodes of Ranvier in sciatic nerves with node-like structures in optic nerves of the mouse. J Biophys Biochem Cytol. 1960 Jul;7:761–762. doi: 10.1083/jcb.7.4.761. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Journal of Cell Biology are provided here courtesy of The Rockefeller University Press

RESOURCES